1. Field of the Invention
The present invention relates to differential drives for a motor vehicle, and more particularly, relates to an active torque transfer device for use in a vehicle.
2. Description of Related Art
The differential drive is well known in the motor vehicle industry. The differential drive is used in conjunction with the transmission and drive shaft or propeller shaft (prop shaft) to turn the automotive vehicle wheels at different speeds when the vehicle is going around a curve, to differentiate the speed of each wheel individually and to provide the proper amount of torque to each wheel in slipping, turning, or other road to wheel conditions.
In a traditional torque on demand drive train layout of an automotive vehicle there is a primary driven front/rear axle and a secondary driven "hang on" axle that is connected via a prop shaft or drive shaft and a torque transfer coupling to the primary driven axle. The torque transfer coupling is usually directly in front of the secondary driven axle. The axle differential creates the division of power (or torque) to each side shaft of the axle. The primary driven axle also includes a differential which divides necessary power to the side shaft of each front axle and then the wheels. The division of torque between the front and rear axle is completed by the torque transfer coupling which is a separate unit on the drive train system and requires space for its housing and other related parts. A current state of the art torque transfer coupling for an automotive vehicle is located between the primary and secondary driven axles of the vehicle and, generally consists of a friction clutch pack which is loaded via a ball ramp mechanism. The ball ramp mechanism is engaged by an electric motor. An electronic control unit senses slip conditions of the wheels, monitors current driving conditions of the vehicle and applies a current to the electric motor which will engage the clutch via the ball ramp mechanism and distribute torque to each wheel as necessary.
An active torque transfer system provides maximum flexibility in the distribution of torque between the axles of an all wheel or four wheel drive automotive system. A similar system can be used in applying torque within an axle on a side to side basis between a left rear wheel and a right rear wheel. Other devices currently used in the art for active torque transfer include electromagnetically engaged pilot clutch to drive a ball ramp mechanism. This mechanism loads the main clutch via electromagnetically engaged pilot clutches. Most of the systems use the same ball ramp mechanism but use different engagement mechanisms to engage the ball ramp mechanism to the clutch unit. All of these active torque drive systems are located in a separate housing usually directly in front of the rear differential in most cases.
Therefore, there is a need in the art for a device to simplify and reduce the weight and required space of an active torque distribution device for use in an automotive vehicle.